I have an aggregation pipeline in which i want to add new field based on certain condition. My pipeline is like this

[
  { // match stage

    $or:[
     { 
       $and: [
         {placement: {'$nin': [-1,-2]}},
         {contract_proposal_metadata : {$exists: true}}
       ]
     },
     { 
       risk_info_request_metadata: {$exists: true}
     }
   ]

  } 
]

Now i want to add a new field record_type based on the condition that if contract_proposal_metadata exists so record type will be 'renewal' and if risk_info_request_metadata is exists then record_type will be request.

How can i achieve this?

CodePudding user response：

You need to use aggregate update

db.collection.update({
      placement: { //Your match goes here
        "$nin": [
          -1,
          -2
        ]
      },
      
    },
    [
      {
        $set: {
          status: {
            $switch: {
              branches: [
                { //update condition goes here
                  case: {
                    $ifNull: [
                      "$contract_proposal_metadata",
                      false
                    ]
                  },
                  then: "renewal"
                },
                {
                  case: {
                    $ifNull: [
                      "$risk_info_request_metadata",
                      false
                    ]
                  },
                  then: "request"
                },
                
              ],
              default: ""
            }
          }
        }
      }
    ],
    {
      multi: true
    })

1. It supported from mongo 4.2
2. $exists cannot be used, hence $ifnull used

playground

CodePudding user response：

You are not adding new field conditionally. You are always adding the field, just with different values.

There is $cond operator which returns 1 of 2 values depending on condition in the first argument.

You already know $exist for the $match stage, and the equivalent operator to use in aggregation expression is $type

[
   { // match stage
       .....
   },
   {  // adding the field
      $addFields: {
          record_type: { $cond: { 
              if: { $eq: [ { $type: "$contract_proposal_metadata" }, "missing" ] }, 
              then: "request", 
              else: "renewal" 
          } }
      }
   }
]